Washers can be categorised into three types;
- Plain washers, which spread a load, and prevent damage to the surface being fixed, or provide some sort of insulation such as electrical
- Spring washers, which have axial flexibility and are used to prevent fastening or loosening due to vibrations
- Locking washers, which prevent fastening or loosening by preventing unscrewing rotation of the fastening device; locking washers are usually also spring washers.ter diameter (OD) about twice their inner diameter (ID), but this can vary quite widely.
Washers are usually metal or plastic. High-quality bolted joints require hardened steel washers to prevent the loss of pre-load due to Brinelling after the torque is applied.